From: matz@... (Yukihiro Matsumoto)
Date: 2003-11-22T08:37:03+09:00
Subject: Re: "stereotyping" (was: Re: Strong Typing (Re: Managing metadata about attribute types) )

Hi,

In message "Re: "stereotyping" (was: Re: Strong Typing (Re: Managing metadata about attribute types) )"
    on 03/11/22, "Weirich, James" <James.Weirich@FMR.COM> writes:

|I've been thinking about DbC stuff for some time and something in Matz Ruby
|2 talk last Saturday sparked an idea along these lines ...
|
|   class Person
|     def greet(other_person)
|       marry(other_person)
|     end
|   end
|
|Then specify the contract in a separate file ...
|
|   class Person
|     def greet:pre(other_person)
|       assert ! self.married?
|       assert ! other_person.married?
|     end
|
|     def greet:post(other_person)
|       assert other_person.married?
|       assert self.married?
|       assert_equal self, other_person.spouse
|       assert_equal other_person, self.spouse
|     end
|   end

I'd be second to Chad.  Cool.

|An aside: Unfortunately, the post method doesn't have access to the result
|returned from the function.  In this case it doesn't matter, but many post
|conditions assert something interesting about the result.  I guess I would
|have to use a wrap method for that.

The only reason the result is _not_ available from post method is we
don't have neat syntax construct.  Any proposal?

							matz.